The present invention relates in general to an animal waste management system and method thereof and more particularly to a hog waste management system and method thereof for waste management systems which provide for continuous recycling of animal waste slurry such that a highly concentrated waste slurry is produced.
Two of the primary systems utilized in the hog industry to remove animal waste from animal confinement barns are the high volume flush system and pull plug system. In high volume flush systems, the water introduced for livestock watering, cleaning, and cooling mixes with solid excrement from the animals to produce a waste slurry. Without dilution, the slurry concentration generated by the hogs ranges from 3-9% total solids depending upon water management practices used by the hog producer. Designed to improve air quality in the confinement barns and to convey manure slurry from the barns, the high volume recycle system intentionally dilutes the waste slurry with recycled surface water from large ambient temperature anaerobic lagoons or other downstream treatment/storage units so that the waste slurry flushed from the barns contains typically less than 0.5% total solids. In pull plug systems, a large volume of pit recharge water is recycled in a similar fashion for similar reasons so that the waste slurry again contains less total solids (typically 0.5-2%) when flushed from the barns.
A problem associated with ambient temperature anaerobic lagoon systems is the accumulation of soluble salts. Long term storage and recycling of lagoon wastewater allows the accumulated liquor to reach saturation in sparingly soluble salts, primarily struvite (magnesium ammonium phosphate). These salts deposit in recycle and recharge pumps and piping systems and require routine removal for proper system operation. The removal of the accumulated salts in conventional systems is very costly. In systems where the problem becomes chronic, the system is often reconfigured to provide two parallel systems so that one can be operated while the other is cleaned with acid to remove the salt deposits.
Flush systems and pull plug systems, use relatively large volumes of dilute recycle/recharge wastewater from down stream treatment/storage processes to convey waste. Thus the flow rates from confinement buildings utilizing these existing technologies are as much as 30 fold higher than the actual slurry production rate of the animals. This low concentration of waste slurry causes prohibitively high capital and operating costs when attempting to retrofit these systems with advanced waste treatment technology. Advanced waste treatment technologies include but are not limited to anaerobic digestion gassification and chemical processing to produce commercially valuable fertilizer, fuel, or other products. The factors resulting in high operating and capital costs include but are not limited to the need for large vessel sizes, slurry temperature loss and high pump volumes. The only viable alternative to alleviate these problems is to modify existing barns with alternative waste collection systems. Until now, most producers could not justify the high cost of a system changeover.
Accordingly, the present invention is directed to overcoming one or more of the problems as set forth above.
An animal waste management system for handling a waste slurry having a plurality of coarse solids contained therein flushed from an animal confinement housing at a flush rate is disclosed. The system comprises separation means for separating the coarse solids from the waste slurry flushed from the animal confinement housing, removal means for removing a volume of the waste slurry produced from the separation means to produce a remaining volume of waste slurry, conditioning means for conditioning the remaining volume of waste slurry from the removal means to maintain air quality in the animal confinement housing, and recycling means for recycling the conditioned waste slurry through the waste management system at a recycle rate, which is preferably at least approximately ninety-five percent of the flush rate, whereby the removed volume of waste slurry has a high concentration of solids. The amount of solids in the removed waste slurry is preferably in the range of approximately four to eight percent. The separation means is preferably selected from the group consisting of a screen, a hydrocyclone, a chemical thickener, and a settling cone.
The conditioning means comprises an aerator adapted to aerate the remaining volume of waste slurry to prevent the formation of hydrogen sulfide, and a regulator adapted to regulate the pH of the remaining volume of waste slurry to prevent the emission of excess ammonia. The removal means comprises sedimentation means to segregate the waste slurry produced by the separation means such that the removed volume of waste slurry is more concentrated than the remaining volume of waste slurry. The sedimentation means is preferably a tank having a lower region and an upper region in which the remaining waste slurry is segregated such that the removed volume of waste slurry is allowed to settle toward the bottom region of the sedimentation tank, and the removal means is a valve or pump in communication with the lower region of the sedimentation tank. The sedimentation means may comprise a controller having a predetermined control level and a valve in communication with the controller, the valve being adapted to open when the level of the remaining waste slurry in the tank is equal to or greater than the predetermined control level and to close or turn off when the level of the remaining waste slurry in the tank is less than the predetermined control level.
The system may further comprise means for mixing the coarse solids separated by the separation means with the removed volume of waste slurry, and a stabilizer in communication with the animal confinement housing and the separation means, the stabilizer being adapted to stabilize the flow of waste slurry through the waste management system. The recycling means may comprise a recycle pump, and the conditioning means may comprise a controller in communication with the recycle pump, the controller being adapted to stop operation of the recycle pump when the level of remaining waste slurry within the conditioning means reaches a predetermined level, whereby failure of the recycle pump is prevented. The system may further comprise processing means for processing the removed waste slurry to produce a plurality of organic materials.
A method for managing a waste produced from an animal confinement housing with a waste management system is also disclosed. The method comprises the steps of flushing the waste from the animal confinement housing with a flushing material at a flush rate to produce a waste slurry having a plurality of coarse solids contained therein, separating the coarse solids from the waste slurry to produce a coarse solids-free waste slurry, removing a volume of coarse solids-free waste slurry to produce a remaining volume of waste slurry, conditioning the remaining volume of waste slurry portion to maintain air quality in the animal confinement house, and continuously recycling the conditioned waste slurry through the waste management system at a recycle rate which is preferably at least ninety-five percent of the flush rate whereby the removed volume of waste slurry has a high concentration of solids. The step of conditioning may comprise the steps of aerating the remaining volume of waste slurry to prevent the formation of hydrogen sulfide, and adjusting the pH of the remaining volume of waste slurry to prevent the emission of ammonia. The method may further comprise the step of segregating the coarse solids-free waste slurry such that the removed volume of waste slurry is more concentrated than the remaining volume of waste slurry. The method may further comprise the step of stabilizing the flow of waste slurry through the waste management system. The waste management system comprises conditioning means, such that the step of recycling comprises pumping the conditioned waste slurry with a recycle pump, and controlling the recycle pump such that operation of the recycle pump is stopped when the level of the remaining volume of waste slurry in the conditioning means reaches a predetermined level. The method may further comprise the step of processing the removed volume of waste slurry.
These and other features of the present invention will be better understood and appreciated from the following detailed description of the following embodiments, selected for the purposes of illustration.